Nanostructures have been found to impart useful properties on surfaces of articles. These useful properties include useful optical properties; such as, for example, reflection reduction of plastic substrates; useful physical properties, such as, for example, surface modification for improved adhesion; and useful structural properties for creating features on surfaces that can be useful in, for example, drug delivery.
A number of methods have been used to produce nanostructures on surfaces of non-(co)polymeric substrates. For example, plasma etching is a useful method that has been used to generate nanostructures. A particular type of plasma etching, reactive ion etching (RIE) has been widely employed in the semiconductor industry to produce submicron features on silicon substrates useful in electronics. Recently, high density plasma processes have been developed that can produce nanostructures on silicon in the sub-100 micrometer range. The semiconductor industry is currently working on the fabrication of nanoscale features on silicon wafers with around 40 nm resolution, using patterning and pattern transfer based on advanced plasma processing tools.
Plasma treatment has also been used to produce antireflective surfaces on (co)polymeric substrates, including transparent (co)polymeric substrates. Many of these treatments are batch processes and can produce only limited antireflective regions on the substrates. Co-pending and commonly assigned PCT Pat. Pub. WO 2011/139593 describes methods to produce nanostructures on surfaces in a substantially continuous manner.